Trojan:W32/DNSChanger will change the infected system's Domain Name Server (DNS) settings in order to divert traffic to unsolicited, and potentially illegal sites.
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Trojan:W32/DNSChanger is a family of malware used by an organized crime syndicate to perpetuate click-fraud, where user's browsing activity is quietly manipulated (such as redirecting a user who clicks on a legitimate link to an unsolicited site) so that the attackers can generate revenue from pay-per-click online advertising schemes.
The trojan is usually a small file (about 1.5 kilobytes) that is designed to change the 'NameServer' Registry key value to a custom IP address. This IP address is usually encrypted in the body of a trojan.
As a result of this change, a victim's computer will contact the newly assigned DNS server to resolve names of different webservers.
This malware is discussed further in the following Labs Weblog post:
Lately we got a few samples of this trojan that were named 'PayPal-2.5.200-MSWin32-x86-2005.exe'. This trojan was programmed to change the DNS server name of a victim's computer to 188.8.131.52 address.
The Registry key that is affected by this trojan is:
Other registry modifications made involve creating these keys: